generate assign stubs for realization and interpretation

[kohlhase]

It would be very helpful, if upon seeing a realization like

\begin{realization}{foo}

the IDE could collect all the symbols of the target (say bar and baz) and generate the

\assign{bar}{???}
\assign{baz}{???}

Even better: it should check which of the assigns are missing and generate stubs only for the missing ones.
There might be better alternatives for the ???, but the functionality would be helpful.

Oh, and of course the analog for {interpretation} as well.

Come to think of it, there are more opportunities for such things as well, e.g.

 \begin{copymodule}{mod?Group/abeliangroup-structure}{addition}

we we can generate something like

    \renamedecl[name=universe]{universe}{universe}